SAMA5D3 Xplained, Issue about SPI interval between each word

[7luck]

Hi guys, i am working on SAMA5D36 Xplained board with SPI accessing to a peripheral device. the SPI works properly, but i found that the interval between each word durning SPI communction is very long. 

my program is based on spidev_test.c and i just made a little bit changes to the spidev_test.c to match my requirements. the SPI protocol driver is the spidev. i use parameters in following to initalize the SPI protocol driver:

         1  Max Speed = 1500 KHz
         2  mode = mode 0 (clock polarity = 0, clock phase =0)
         3  bit per word = 8
         4  no delay between tranfers
         5  msb